The isoenzyme composition of liver pyruvate kinase from hens in ontogeny]

Only one isozyme M2 of pyruvate kinase was found in the liver of hens at all stages of embryonic and postembryonic development. No analogue to isozyme L from the liver of mammals was found. During embryogenesis and postnatal life, isozyme M2 is presented by two forms which differ in pI values. Throughout embryonic and postembryonic development, pyruvate kinase is presented by two forms which differ in their substrate affinity.     

Soluble and Particulate Forms of Rat Catechol-O-Methyltransferase Distinguished by Gel Electrophoresis and Immune Fixation

Catechol-O-methyltransferase (COMT) was visualized in homogenates and subcellular fractions of rat tissues, including liver and brain, by gel electrophoresis, electrophoretic transfer of proteins to nitrocellulose (Western blotting), and immune fixation with antiserum to highly purified soluble rat liver COMT. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of all tissue homogenates examined revealed three major immune-specific proteins with apparent molecular weights 23,000, 26,000, and 66,000 (23K, 26K and 66K). Centrifugation of homogenates at 100,000 X g for 60 min resulted in the enrichment of the 26K species protein in the pellet whereas the 23K and 66K proteins were the predominant forms in the supernatant. The 66K protein appeared in variable amounts depending on the tissue being examined and the length of transfer of protein and is assumed to be an "aggregate" of the smaller form(s). The 26K protein was essentially the only immunoreactive species seen in a purified preparation of rat liver outer mitochondrial membrane. Isoelectric focusing (IEF) under denaturing conditions and two-dimensional gel electrophoresis of brain and liver fractions showed that the 23K protein was resolved into three bands of pI 5.1, 5.2, and 5.3, whereas the 26K protein had a pI of 6.2. Analysis of COMT activity in slices from nondenaturing IEF gels indicated that the pI 5.1-5.3 species are biologically active; the pI 6.2 species could not be detected under these conditions. COMT activity was demonstrated, however, in outer mitochondrial membranes from rat liver, which contain predominantly the 26K, pI 6.2 immunoreactive species. The major form of COMT in all rat tissues examined is "soluble" with an apparent Mr of 23K and a pI of 5.2. The nature of the modifications giving rise to pI 5.1 and 5.3 forms of this enzyme are not clear, nor is the relationship between the 23K and 26K forms. Further studies are needed to elucidate the relationship of immunoreactive forms of COMT to each other, their intracellular location, and their functional significance.     

Multiple molecular forms of the gibberellin-induced alpha-amylase from the aleurone layers of barley seeds

A class of plant growth regulators, gibberellins, induce the synthesis of alpha-amylase (1,4-alpha-D-glucan glucanohydrolase, EC 3.2.1.1) in the aleurone layers of barley (Hordeum vulgare L. var. Himalaya) seeds. The purified alpha-amylase is composed of multiple isozymic forms with indistinguishable molecular weights, but different net charges. These alpha-amylase isozymes separate on isoelectric focusing gels into two groups, each containing multiple species. One group has an apparent isoelectric point (pI) of approximately 5.8 (the high pI group). The other group's pI values are around 4.5 (the low pI group). On some gels a small amount of protein focuses between the high and low pI isozymes. These proteins comigrate with the low pI isozymes upon reelectrophoresis. The synthesis of these two groups is temporally regulated. The high pI group is the dominant set of isozymes secreted from embryoless half seeds during the first two days of gibberellin administration. After four days, however, the major isozymes are those of the low pI group. This shift in isozyme pattern is due to a shift in their relative rates of synthesis. Peptide analysis of these two groups of isozymes with Staphylococcus aureus V8 protease and cyanogen bromide shows amino acid sequence differences. However, members within the same group have similar peptide patterns. Both groups of isozymes are synthesized in vitro in a wheat germ extract primed with poly(A)+ RNA isolated from gibberellin-treated aleurone layers. This indicates that the synthesis of the two groups of alpha-amylase isozymes is probably directed by two or more different populations of mature mRNA. A model that explains these observations and the available genetic information is that barley aleurone alpha-amylase isozymes are encoded by at least two sets of structural genes.     

The analysis of mammalian development using allelic isozyme variants

The past decade has seen an explosion of interest in mammalian embryos. Techniques of molecular and genetic analysis coupled with advances in in vitro culture and experimental manipulation of mammalian embryos have provided important insights into mechanisms of embryogenesis. Many of these recent advances have been facilitated by the use of allelic isozyme variants as autonomous cell markers or representative gene products. Investigations aimed at exploring cell lineages and cell commitment, the timing and regulation of gene expression, X chromosome inactivation, and cell interactions have depended on the availability of appropriate isozyme variants. Results from such experiments are summarized here in order to demonstrate the usefulness of this approach and to stimulate its wider application in developmental biology.     

Isoelectric focusing studies of aldehyde dehydrogenases from mouse tissues: variant phenotypes of liver, stomach and testis isozymes

Isoelectric focusing techniques (IEF) were used to examine the tissue distribution and genetic variability of aldehyde dehydrogenases (AHDs) from inbred strains of mice. Twelve zones of AHD activity were resolved which were differentially distributed between tissues. Liver extracts exhibited highest activity for most enzymes, with the exception of isozymes found in stomach (AHD-4) and testis (AHD-4 and AHD-6). Genetic variants for AHD-1 (liver mitochondrial isozyme) and AHD-4 (stomach isozyme) were examined from inbred strains and F1 hybrid animals. The results were consistent with dimeric subunit structures (designated as A2 and D2 isozymes respectively). IEF patterns for activity variants of testis-specific AHD-6 were identical, with 3-banded phenotypes being observed. pI values for the AHD forms as well as for aldehyde oxidase and xanthine oxidase isozymes, which stain in the absence of coenzyme, were reported.     

Kraft Pulp Bleaching and Delignification by Dikaryons and Monokaryons of Trametes versicolor

The ability of 10 dikaryotic and 20 monokaryotic strains of Trametes (Coriolus) versicolor to bleach and delignify hardwood and softwood kraft pulps was assessed. A dikaryon (52P) and two of its mating-compatible monokaryons (52J and 52D) derived via protoplasting were compared. All three regularly bleached hardwood kraft pulp more than 20 brightness points (International Standards Organization) in 5 days and softwood kraft pulp the same amount in 12 days. Delignification (kappa number reduction) by the dikaryon and the monokaryons was similar, but the growth of the monokaryons was slower. Insoluble dark pigments were commonly found in the mycelium, medium, and pulp of the dikaryon only. Laccase and manganese peroxidase (MnP) but not lignin peroxidase activities were secreted during bleaching by all three strains. Their laccase and MnP isozyme patterns were compared on native gels. No segregation of isozyme bands between the monokaryons was found. Hardwood kraft pulp appeared to adsorb several laccase isozyme bands. One MnP isozyme (pI, 3.2) was secreted in the presence of pulp by all three strains, but a second (pI, 4.9) was produced only by 52P. A lower level of soluble MnP activity in one monokaryon (52D) was associated with reduced bleaching ability and a lower level of methanol production. Since monokaryon 52J bleached pulp better than its parent dikaryon 52P, especially per unit of biomass, this genetically simpler monokaryon will be the preferred subject for further genetic manipulation and improvement of fungal pulp biological bleaching.     

Amino acid sequence of rhizopuspepsin isozyme pI 5

The complete amino acid sequence of an aspartic protease from Rhizopus chinensis, rhizopuspepsin isozyme pI 5, has been determined. Partial sequences were first obtained from the isolated isozyme by a combination of chemical and proteolytic enzyme cleavages, peptide purifications, and Edman degradations. About one-half of the sequence was revealed by this approach. To complete the amino acid sequence, a cDNA library of R. chinensis in pBR322 was constructed. An oligonucleotide probe was synthesized based on the sequence Trp-Trp-Gly-Ile-Thr, and about 40 positive clones were identified by colony hybridization. A clone, 33E2, which had an insert size of about 1.1 kilobase pairs, was found to contain the entire coding region of rhizopuspepsin isozyme pI 5. The sequence of rhizopuspepsin contains 325 amino acid residues. The alignment of the rhizopuspepsin sequence against other aspartic proteases revealed expected homology, with the closest similarity to penicillopepsin which shares 39% identical residues. Porcine pepsin shares about 36% identical residues with rhizopuspepsin.     

Detection and Characterization of Some New Basic Proteins in Chicken Postsynaptic Densities

Chicken brain postsynaptic density (PSD) polypeptides, obtained by treating synaptosomes with 0.5% Triton X-100 and then further purified on a sucrose gradient, are demonstrated to contain four basic proteins of 76K (pI greater than 9.2), 58K (pI 8.1-8.8, heterogeneous), 40K (pI 9.0), and 24K (pI 8.9). Nonequilibrium pH gradient-sodium dodecyl sulfate two-dimensional gels further reveal six more basic proteins with pI values higher than 9.2: 76K, 52K, 47K, 45K, 36K, and 34K. These basic proteins are a major part of the total chicken PSD polypeptides appearing on the gels. Some of these basic proteins (58K, 52K, 47K, 36K, 24K, and two at 76K) are distinguishable from those of brain mitochondria, the major contaminant. The 40K and 34K proteins may be common mitochondrial polypeptides. The 45K protein is probably a mitochondrial contaminant. A number of proteins including 76K (synapsin I-like protein) and 58K, along with some other minor ones, can be phosphorylated by endogenous protein kinase(s) in the presence of Ca2+, Mg2+, and [gamma-32P]ATP. No PSD basic proteins bind Ca2+.     

菜心中高等电点高活性的乙醇酸氧化酶同工酶的纯化和特性

乙醇酸氧化酶 (EC 1 1 3 15 ,GO)被认为只含4 0kD一种碱性亚基 ,是因为从多种植物中获得了具GO活性的蛋白 ,SDS PAGE后呈约 4 0kD单带[1] .菠菜GOcDNA编码约 370个氨基酸 ,即 4 0kD多肽 ,其碱 酸性氨基酸的比例高达 0 96 ,富含碱性氨基酸[2 ] .已克隆的GOcDNA在E .coli中表达     

Heterogeneity and regulation of manganese peroxidases from Phanerochaete chrysosporium.

Lignin and Mn peroxidases are two families of isozymes produced by the lignin-degrading fungus Phanerochaete chrysosporium under nutrient nitrogen or carbon limitation. We purified to homogeneity the three major Mn peroxidase isozymes, H3 (pI = 4.9), H4 (pI = 4.5), and H5 (pI = 4.2). Amino-terminal sequencing of these isozymes demonstrates that they are encoded by different genes. We also analyzed the regulation of these isozymes in carbon- and nitrogen-limited cultures and found not only that the lignin and Mn peroxidases are differentially regulated but also that differential regulation occurs within the Mn peroxidase isozyme family. The isozyme profile and the time at which each isozyme appears in secondary metabolism differ in both nitrogen- and carbon-limited cultures. Each isozyme also responded differently to the addition of a putative inducer, divalent Mn. The stability of the Mn peroxidases in carbon- and nitrogen-limited cultures was also characterized after cycloheximide addition. The Mn peroxidases are more stable in carbon-limited cultures than in nitrogen-limited cultures. They are also more stable than the lignin peroxidases. These data collectively suggest that the Mn peroxidase isozymes serve different functions in lignin biodegradation.     

Characterization of the oxycomplex of lignin peroxidases from Phanerochaete chrysosporium: equilibrium and kinetics studies

The oxycomplexes (compound III, oxyperoxidase) of two lignin peroxidase isozymes, H1 (pI = 4.7) and H8 (pI = 3.5), were characterized in the present study. After generation of the ferroperoxidase by photochemical reduction with deazoflavin in the presence of EDTA, the oxycomplex is formed by mixing ferroperoxidase with O2. The oxycomplex of isozyme H8 is very stable, with an autoxidation rate at 25 degrees C too slow to measure at pH 3.5 or 7.0. In contrast, the oxycomplex of isozyme H1 has a half-life of 52 min at pH 4.5 and 29 min at pH 7.5 at 25 degrees C. The decay of isozyme H1 oxycomplex follows a single exponential. The half-lives of lignin peroxidase oxycomplexes are much longer than those observed with other peroxidases. The binding of O2 to ferroperoxidase to form the oxycomplex was studied by stopped-flow methods. At 20 degrees C, the second-order rate constants for O2 binding are 2.3 X 10(5) and 8.9 X 10(5) M-1 s-1 for isozyme H1 and 6.2 X 10(4) and 3.5 X 10(5) M-1 s-1 for isozyme H8 at pH 3.6 and pH 6.8, respectively. The dissociation rate constants for the oxycomplex of isozyme H1 (3.8 Z 10(-3) s-1) and isozyme H8 (1.0 X 10(-3) s-1) were measured at pH 3.6 by CO trapping. Thus, the equilibrium constants (K, calculated from kon/koff) for both isozymes H1 (7.0 X 10(7) M-1) and H8 (6.2 X 10(7) M-1) are higher than that of myoglobin (1.9 Z 10(6) M-1).(ABSTRACT TRUNCATED AT 250 WORDS)     

Gene Expression in Developing Zea mays Embryos: Regulation by Abscisic Acid of a Highly Phosphorylated 23- to 25-kD Group of Proteins

We have earlier identified a set of proteins of 23 to 25 kilodaltons (kD), covering an isoelectric point (pI) range of 6.2 to 8.2, which accumulate gradually during normal embryogenesis of Zea mays and disappear in early germination. These polypeptides can be induced prematurely in immature embryos by abscisic acid (ABA) treatment. We report here that the more acidic protein forms are due to post-translational phosphorylation of at least two polypeptides of 23 kD, pI 8.2 and 25 kD, pI 8.0. A polyclonal antiserum was obtained which recognizes all forms of both the 23-kD and 25-kD polypeptides. Recovery of cDNA clones corresponding to these proteins was accomplished by hybridization with cDNA made from size-selected mRNA enriched for these sequences. Hybrid selection experiments demonstrate that clone MA12 specifically hybridizes with mRNAs encoding the 23-kD and 25-kD protein set which are recognized by the antiserum. By Northern hybridization analysis, the RNA encoded by clone MA12 is shown to accumulate in mature embryos and to be induced in young embryos upon ABA incubation.     

Reversal of relative proteinase F activity and onset of androgen-dependent proteinases in the submandibular gland of postnatal mice

By isoelectric focusing, we separated trypsin-like proteinases of the mouse submandibular gland (ICR strain) into isozymes with pI values of 4.6 (proteinase F), 5.6 (protease D), 5.8 (protease A), 7.1 and 9.9 (P-esterase). During postnatal development, proteinase F appeared earliest (on the 15th day after birth) and increased in both sexes; however, its percentage ratio to total activity decreased markedly with time because of the rapid increase of other proteinases. On the 22nd day of life, proteinases A and D appeared, and the increase of a proteinase with pI-7.1 followed thereafter. P-esterase was the last isozyme to appear, becoming detectable around 29-45 days. After maturation, the activities of protease A plus D, P-esterase, and the isozyme with a pI value of 7.1 were higher in males than in females, whereas the relative level of proteinase F was reversed. We conclude that proteinase F is appreciably different from the other four proteinases in its development pattern as well as in its responsiveness to sexual hormones.     

Phosphorylation of lignin peroxidases from Phanerochaete chrysosporium. Identification of mannose 6-phosphate

Many of the extracellular lignin-degrading peroxidases from the wood-degrading fungus Phanerochaete chrysosporium are phosphorylated. Immunoprecipitation of the extracellular fluid of cultures grown with H2K32PO4 with a polyclonal antibody raised against one of the lignin peroxidase isozymes, H8 (pI 3.5), revealed the incorporation of H2K32PO4 into lignin peroxidases. Analyses of the purified isozymes from labeled cultures by isoelectric focusing showed that, in addition to isozyme H8, lignin peroxidase isozymes H2 (pI 4.4), H6 (pI 3.7), and H10 (pI 3.3) are also phosphorylated. These analyses also showed that lignin peroxidase isozyme H1 (pI 4.7) and manganese-dependent peroxidase isozymes H3 (pI 4.9) and H4 (pI 4.5) are not phosphorylated. Phosphate quantitation indicated the presence of one molecule of phosphate/molecule of enzyme for all of the phosphorylated isozymes. To locate the site of phosphorylation, one-dimensional phosphoamino acid analysis was performed with hydrolyzed 32P-protein. However, phosphotyrosine, phosphoserine, and phosphothreonine could not be identified. Coupled enzyme assays of acid hydrolysate indicated the presence of mannose 6-phosphate as the phosphorylated component on the lignin peroxidase isozymes. Digestion of the isozymes with N-glycanase released the phosphate component, indicating that the mannose 6-phosphate is contained on an asparagine-linked oligosaccharide.     

Thymidine kinase enzyme variants in Physarum polycephalum. In vitro interconversion of the enzyme variants.

Isoelectric focusing of plasmodial extracts of Physarum polycephalum demonstrated the presence of several multiple enzyme variants of thymidine kinase, which appear sequentially during the nuclear division cycle. Variants (A) + (A1) are the only enzyme variants found in the late G2-phase, whereas the variants (C) + (C1) are only present at the time of mitosis and S-phase (1, 2). Evidence is presented that multiple forms of thymidine kinase (A) + (A1) with high pI arise by dephosphorylation of a primary translation product with low pI (C and/or C1). The thymidine kinase fractions (A) + (A1) and (C) + (C1) + (c1) were separated and partially purified by DEAE-cellulose chromatography. The enzyme variants (C) + (C1) are converted in vitro by an endogenous enzymatic factor as well as by bacterial alkaline phosphatase into the variants (A) + (A1).     

Prothrombin biosynthesis: characterization of processing events in rat liver microsomes

Plasma and hepatic microsomal forms of rat prothrombin have been compared by sodium dodecyl sulfate-polyacrylamide electrophoresis and isoelectric focusing. The major prothrombin species that accumulated in the microsomes of rats treated with warfarin had a molecular weight of 78 500 and a pI in 8 M urea of 6.3-6.5. Plasma prothrombin had a molecular weight of 83 500 and a pI of 5.3-5.7. Microsomes from normal rat liver contain a second pool of precursor with a molecular weight of 83 500, and digestion with the glycosidase Endo H indicated that this form has been processed to contain complex carbohydrates, while the Mr 78 500 form is a high mannose form and is the substrate for the vitamin K dependent carboxylase. Treatment of rats with tunicamycin revealed that glycosylation was not essential for carboxylation or secretion from the liver. Comparison of the aglyco forms of prothrombin and its precursors suggests that the intracellular forms contain a basic, Mr approximately 1500 peptide that is missing from the plasma form of prothrombin.     

Multiplicity of liver microsomal flavin-containing monooxygenase in the guinea pig: its purification and characterization

Two distinct forms (FMO-I and FMO-II) of flavin-containing monooxygenase were purified from the liver microsomes of guinea pig. The minimum molecular weights estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis were 54,000 for FMO-I and 56,000 for FMO-II, respectively. Tryptic digestion of these enzymes gave different electrophoretic patterns, suggesting that FMO-I and -II have distinct amino acid sequences. The amino terminal sequence of FMO-II could not be estimated probably due to its blocking while that of FMO-I was determined to be highly homologous to the rabbit liver flavin-containing monooxygenase (J. Ozols, 1989, Biochem. Biophys. Res. Commun. 163, 49-55). Absorption maxima of FMO-I and -II were recorded at 368 and 440 nm and 381 and 456 nm, respectively. Molar ratios of FAD to both of these apoenzymes were shown to be one to one. Substrate specificity of FMO-I and -II was determined using 15 compounds as the substrate. The results showed two enzymes that exhibited overlapped but different specificity toward these substrates although FMO-I had lower activity than did FMO-II with all compounds except thiobenzamide. Of particular interest, only FMO-II showed considerably high activities for primary amines, n-octylamine, and n-decylamine. Immunoglobulin G raised against FMO-II could recognize FMO-I as well as FMO-II, but the reactivity of FMO-I toward the antibody was obviously lower than that of FMO-II. Electrophoresis followed by immunostaining revealed that microsomes of lung, kidney, urinary bladder, testis, and spleen contain the same protein as FMO-II and/or FMO-I. Only lung was shown to have an additional isozyme of FAD-monooxygenase with a molecular weight apparently higher than those of FMO-I and -II. These results strongly suggest that at least two forms of flavin-containing monooxygenases distinct from the lung-type isozyme are expressed in liver of guinea pigs.     

Effect of cultivation age and embryo size on specific oxygen uptake rate in developing somatic embryos ofDaucus carota L.

Summary The average specific oxygen uptake rate of carrot (Daucus carota L.) somatic embryos in batch culture decreased with cultivation time, coinciding with an increase in the size and maturity of the embryos. From experiments performed on three size classes obtained at 15 days of culture, larger embryos were found to have a lower oxygen uptake rate suggesting either a lower intrinsic metabolic activity and/or transport limitations leading to a reduction in the observed metabolic activity.     

Variation and morphogenetic characteristics of different Stachys species during microclonal propagation

Morphogeneses of Stachys different species introduced in culturing in vitro have been compared. The frequency of altered forms have been demonstrated to be related to the plant genotype. All regenerants of S. sieboldii, which reproduces in vivo only vegetatively, are phenotypically normal, irrespective of the concentrations of plant growth regulators at which they have been obtained. Only changes in isozyme patterns have been observed in the regenerants grown in media containing at least 10 mg/l benzyl aminopurine (BAP); most of these changes are the absence of a particular component of the pattern. The cross-pollinating species Stachys ocymastrum, which typically reproduces by seeds, has yielded morphologically altered forms even in phytohormone-free media; its isozyme patterns often contained a new component. Analysis of the isoperoxidase patterns of regenerants of both Stachys species obtained with the use of high phytohormone concentrations has demonstrated qualitative and quantitative changes suggesting the appearance of somaclonal variants even in the course of plant regeneration directly from nodal segments, bypassing callus formation. Changes have also been found in Stachys plants regenerating from the callus tissue.